Astronomy Rewind: April 2019

The threshold to spring and wistful nostalgia, this April was a month that was beautiful not merely Earth-wise, but celestially, too. From the iconic black hole image that made headlines to rainfall on the Sun (yes, you saw that right), read on to find more about the fascinating happenings in the world (or rather, the universe?) of astrophysics that took place over the past one month.

Top News

It’s Raining on the Sun and We’re Not Joking!

The Sun is probably the last place in the solar system where you would expect it to rain, and this is not anything ordinary. It’s perhaps one of those times the plasma in the Sun’s corona thought why should water have all the fun! While water condenses because of lower temperatures, the plasma cools down as it traces strong magnetic field lines eventually falling back to the surface, a phenomenon our friends at NASA call, ‘The Coronal Rain’.

Credits: NASA’s Solar Dynamics Observatory/Scientific Visualization Studio/Tom Bridgman, Lead Animator

Talking about magnetic field lines, those surrounding the sun are specific structures called ‘Helmet Streamers’ which are closed magnetic loops that can be seen during a solar eclipse. It seems obvious that one should be able to find coronal rain here and that’s precisely what NASA has been looking for a very long time, except that now they’ve found something else, rain on the open field lines!

This seemingly unlikely observation was attempted to be explained using the phenomenon of magnetic reconnection. These measurements could someday help scientists answer a few mysteries about the Sun that has been haunting us for decades, like why the Sun’s corona is much hotter than the surface, and the origin of slow solar winds. Scientists expect data from the Parker Solar Probe to help further in understanding their observations (more on that later).

The Universe’s First Molecule

NASA’s SOFIA- Stratospheric Observatory for Infrared Astronomy — has certainly lived up to its name (It means ‘wisdom’ in Greek) and has added to our knowledge of the cosmos. With several notable achievements since its launch, such as capturing the birth of several enormous stars in the W51 stellar cloud, the Boeing aircraft fitted with a telescope has constantly brought wondrous phenomena to light. Now, it has turned its gaze to the deep past and has successfully detected the first type of molecule to ever form in the universe, helium hydride, formed from two of the lightest and most abundant elements present. Though its existence in nebulae was predicted in the 1970s, this ion eluded scientists for two reasons: the radiation it emits cannot pass through the Earth’s atmosphere and the instruments in use then were not attuned to its specific frequency. However, with the latest upgrade added to the SOFIA observatory, a channel (similar to a radio receiver, as clarified by NASA) that is set to the spectral line of helium hydride, HeH+ finally emerged as a clear signal, validating scientists’ predictions about the early behaviour of the universe. This also paves the way for them to reconstruct the origins of the more complex molecules we see now from their primitive components.

Discrepancies with the Hubble Constant

One of Edwin Hubble’s most astounding discoveries was that the universe is expanding and the farther a galaxy is from Earth, the faster it appears to be moving. The rate of this expansion is known as the Hubble Constant. This long sought after number could help us estimate the size and age of the universe. But, as with most things in the field of astronomy, there is a problem. Depending on the way you calculate the constant, the value changes. This month, new data from the Hubble Space Telescope suggest that this discrepancy is not a fluke! The study uses Cephid Variables, a pulsating star, in the Large Magellanic Cloud, a nearby Satellite galaxy. Cephids brighten and dim at predictable rates, which allows us to calculate their luminosity and therefore distance. We can find the distance to the Large Magellanic Cloud by observing the dimming of light as one star passes in front of its partner in a binary star system. This accurate approach suggests the Universe’s expansion at 74 kilometres per second per megaparsec, a far cry from the 67 kilometres per second per megaparsec calculated from cosmic microwave background. This is exciting for physicists who now need to work on new physics to explain the disparity between the expansion rate of the early universe and that of today.

Mars’s Methane Mystery

(Image courtesy:

Methane — four hydrogens attached to a single carbon atom — is the simplest molecule in the entirety of organic chemistry. Yet it is one of the many mysteries of this vast universe which is baffling us for decades. This time, it concerns methane in the Martian atmosphere. Methane is important to scientists, as it is produced by both biological (cow farts) and abiological (volcanoes) processes. In other words, studying methane on Mars helps us answer a very important question:

“Is there life on Mars?”

First, methane has a very short life span on Mars due to ultraviolet radiation from the sun. Hence, the existence of methane is itself a topic of debate in the scientific community. Over the decades, we are observing variations in levels of methane in the Martian atmosphere. In the 2nd week of April, we received data from the European Space Agency’s ExoMars Trace Gas Orbiter. Methane was one of the trace gases studied. Its first report of Martian atmosphere observed by two spectrometers called NOMAD and ACS found an upper limit of methane 10–100 times less than all previously reported detections. Around 20 years ago, observations indicated up to 50 ppbv (parts per billion by volume) methane. But in 2004, Mars Express reported early measurements up to only 30 ppbv. But in 2013, Curiosity rover on the surface detected a methane spike of 6 ppbv. But in orbit, Mars Express did not find any methane from 2012 to 2014, except a spike one day after Curiosity detected methane. And now, our most precise measurements of methane in the Martian atmosphere are about 0.05 ppbv only. This is a serious issue for scientists, as we have observed the absence of methane which does not reconcile with any of the previous datasets. Also, we need to find what processes destroy methane near the Martian surface.

“Just as the question of the presence of methane and where it might be coming from has caused so much debate, so the issue of where it is going, and how quickly it can disappear, is equally interesting,”

Håkan Svedhem, ESA’s TGO project scientist

It is clear that we do not know the whole picture yet, but we have better instruments, and better technology now. We can assure ourselves that as we get more data, we can resolve this mystery someday.

Space Mission Updates


(Image credits:

Sol 128 for InSight was a special day. It recorded the first potential Marsquake. Check it out in this Youtube video:

The Seismic Experiment for Interior Structure (SEIS) is a special instrument deployed on to the Martian surface that’s on the lookout for special waves, like the ones of seismic origin. By studying the properties of the waves that are beamed back by the instrument, scientists can determine the nature of the matter that the waves have passed through.

Parker Solar Probe

Speaking of the Parker Solar Probe, look who’s made a closer-than-ever-before approach to our parent star! On 4 April, the spacecraft flew within 15 million miles of the Sun, gathering valuable scientific data. According to the Johns Hopkins Applied Physics Laboratory, contact was established with the probe satisfactorily and all instruments seem to be in working order. Good to hear!

Habayusa2 and the ‘Small Carry-on Impactor’ Experiment

Humans love leaving a mark. From flags on the moon to cars in space, we have proven again and again that the sky is the limit. On April 5, humans exchanged roles by leaving a mark on an asteroid for the very first time. Japan’s Habayusa2 conducted an experiment fondly known as Small Carry-on Impactor. The surface of the 900-m diameter asteroid, Ryugu, was hit by a 2.5 kg copper projectile at a velocity of 2 km/s. The team waited a few weeks to look at the crater, fearing ejecta could be in orbit around the asteroid which could cause harm to the spacecraft. A few weeks later we saw some stunning images of the man-made crater. The impact had a diameter of 20 meters, much larger than expected. Valuable samples after the blast will be collected by Hayabusa. This means we could soon have our hands on parts of the asteroid, below the surface, untouched by cosmic radiation.

April Bonus

How Does the ISS Aid Humanity?

NASA has published a new book and it’s overwhelming. The ISS is a perfect example of international collaboration for scientific progress. This multi-billion-dollar project is a true testament to human prowess and our insatiable curiosity towards unwinding the secrets of the universe. But, that’s not all that the ISS is good for. Experiments and research conducted at the ISS have played an invaluable role in aiding humanity alike in multiple sectors.

(Image credits:

We are not going to spoil it for you here. Grab your copy of NASA’s “International Space Station Benefits for Humanity” now to find out more!


The Pseudo-Eye of Sauron Takes Over The Internet

Sometimes, it so happens that something spectacularly brilliant takes place, so brilliant that all of humanity can do nothing but watch in utmost awe. And many of the times, it involves the cosmos choosing to shyly, playfully unveil a part of itself, further entrancing this species into helplessly persisting on the eternal quest for knowledge.

On April 10, one such event happened. To bated breath and relentless curiosity, scientists of the Event Horizon Telescope (EHT) released a very iconic photograph, the subject of which is the supermassive black hole looming deep in the heart of the galaxy we know as M87. Yes, a real picture of a black hole!

First things first. The EHT is not a single device in some corner of the world, but a network of 8 globally scattered telescopes, working together as a planet-wide ‘telescope’ that possesses previously unachieved levels of sensitivity and resolution. To capture such an elusive object located some 55 million light-years away would understandably need the best resources available.

“Taking a picture of a black hole” makes as much sense as trying to photograph a black cat in the darkest ever cellar without the aid of a flashbulb. In reality, what we try to capture is not the image of the black hole itself, but its effects on the surrounding matter and light.

The radio data gathered from the eight telescopes were synchronised and brought together by a technique known as very-long-baseline interferometry. I promised the editor not to delve too deep into jargon and put readers to sleep, so look that up yourself if you’re interested. Stitching together data is an important part of any astronomical imaging process, and this one was no exception with specialised algorithms put to use for the purpose.

And finally, voila! Here’s the much-coveted, prophesied-for-ages image for humans to swoon over (and make memes on).

(Image credits: Wikipedia)

The dark portion in the middle of the bright ring is the ‘silhouette’ of the black hole against the backdrop of brighter matter.

The EHT continues to collect data for further research, and future work is said to involve the Sagittarius A* black hole, situated at the centre of our own galaxy.

Just one century ago, researchers set sail to witness a total solar eclipse with the hope of observing Einstein’s theory of general relativity at work. Today, their occupational descendants have surmounted all previous discoveries solely through the power of mutual collaboration and undying passion for what they do.

I could go on and on, but to do justice to this historical breakthrough, one little section of the Rewind is simply not enough. So stay tuned! ;)

Meanwhile, check out this TEDx talk by Katie Bouman in 2017 about imaging a black hole, and read this piece on the official EHT website.

Image of the Month

While the black hole picture got its well-deserved spotlight, our pick for April is this gorgeously breathtaking visual of M75, a globular cluster located in the constellation of Sagittarius. With over 400,000 stars at its core, this one’s a true spectacle to gaze at.

Image credit: ESA/Hubble & NASA, F. Ferraro et al.

Wonder Junkie This Month

Jeremiah P. Ostriker

“If you take a galaxy and try to make it bigger, it becomes a cluster of galaxies, not a galaxy. If you make it smaller than that, it seems to blow itself apart.”

— Dr Jeremiah P. Ostriker

(Image Courtesy:

The world of theoretical physics is vast and being continuously explored. Here we present to you this month’s astronomer who is a real-life Sheldon Cooper in the field of theoretical astronomy, specialising in cosmology.

Theoretical astronomy is the field that uses analytical models of physics and chemistry to describe astronomical objects and astronomical phenomena. Cosmology is a branch of astronomy that involves the genesis and expansion of the universe, from the Big Bang theory to the present day scenario, extending into the future. Quoting NASA, cosmology is “the scientific study of the large scale properties of the universe as a whole.”

Ostriker has delved into multiple mysteries of the universe, inclusive of the structure and oscillations of rotating stars, the stability of galaxies, the evolution of globular clusters and other star systems, pulsars, X-ray binary stars, the dynamics of clusters of galaxies, gravitational lensing, astrophysical blast waves, active galactic nuclei, the cosmic web, and galaxy formation. His research also extends to dark matter and dark energy, the Warm-Hot Intergalactic Medium (WHIM), galaxy formation and black hole growth and interaction between quasars and their surroundings.

Ostriker is the recipient of several accolades. Some of these include the 2015 Gruber Cosmology Prize, The White House Champions of Change award in 2013, the James Craig Watson Medal in 2012, the Catherine Wolfe Bruce Gold Medal in 2011, the Royal Astronomical Society Gold Medal in 2004, the Golden Plate Award of the American Academy of Achievement in 2001 and the US Medal of Science in 2000. He is a man who continues to inspire and encourage students pursuing astronomy through his words, his works, and his scholarships.

Pop Review

Astronomy has often formed the crux of human reveries from time immemorial and today the folklore and pop culture associated with it roots as deep as space itself. Here, we introduce a new section in Astronomy Rewind, ‘Pop Review’, where we discuss the most happening fictional references and trending pop culture of the previous month! Together let’s share a chuckle with a few snippets of intriguing stuff.

Of course, how can we miss out on Avengers: End Game. As phenomenal as it was, the movie had quite a bit of time and space traveling (oops, spoiler alert!). Are you as baffled as us about the space science behind the Marvel Cinematic Universe? Well, that’s a topic worth an entire article in itself. Here’s a little easter egg, you might get an exclusive soon!

Stay tuned for the next edition of Rewind with more exciting stories and do follow us on social media for some interesting updates!

This article is a culmination of efforts by Aditya_XQ, Anagha Sethuraman, Anumeena Sorna, Atharva Kumar Kulkarni, Nivetha Balu, Pavan Bhushan, ATOTMYR (Sahil) and Vaishnavi Murali.



Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store
Nakshatra NITT

Nakshatra NITT

A student-run university-wide organization for sparking awareness and fascination in astronomy. Interested contributors can contact us by email.