Astronomy Archives

September 12, 2023September 12, 2023 by Evan Gough

The Hubble Imaged Some Globular Clusters in an Unusual Place: Near the Milky Way’s Centre

Most globular clusters are found in the Milky Way's halo. But some, like the glittering globular cluster Terzan 12, are near the galactic centre. Image Credit: ESA/Hubble & NASA, R. Cohen (Rutgers University)

Our galaxy has about 200 Globular Clusters (GCs,) and most of them are in the galaxy’s halo. Astronomers think most GCs were taken from dwarf galaxies and merged with the Milky Way due to the galaxy’s powerful gravity. That explains why so many of them are on the outskirts of the galaxy. But they’re not all in the halo. Some are towards the Milky Way’s galactic bulge. What are globular clusters doing there?

September 11, 2023September 21, 2023 by Evan Gough

JWST Accidentally Found 21 Brown Dwarfs

This artist's conception illustrates the brown dwarf named 2MASSJ22282889-431026, observed by NASA's Hubble and Spitzer space telescopes. Brown dwarfs are more massive and hotter than planets but lack the mass required to become stars. Image credit: NASA

When you launch humanity’s most powerful telescope, you expect results. The JWST has delivered excellent results by detecting ancient galaxies, identifying chemicals in exoplanet atmospheres, and peering into star-forming regions with more detail and clarity than any other telescope.

But every time a new telescope is about to enter service, astronomers tell us they’re excited not only about the expected results but also about the surprising results. And like other telescopes, the JWST has also delivered some surprises. While going about its business, the JWST has discovered 21 brown dwarfs.

September 10, 2023September 10, 2023 by Matt Williams

Polaris is the Closest, Brightest Cepheid Variable. Very Recently, Something Changed.

View from within the Polaris triple star system; artist's rendering. The North Star is labeled Polaris A. Credit: NASA/ESA/HST, G. Bacon (STScI)

When you look up in the night sky and find your way to the North Star, you are looking at Polaris. Not only is it the brightest star in the Ursa Minor constellation (the Little Dipper), but its position relative to the north celestial pole (less than 1° away) makes it useful for orienteering and navigation. Since the age of modern astronomy, scientists have understood that the star is a binary system consisting of an F-type yellow supergiant (Polaris Aa) and a smaller main-sequence yellow dwarf (Polaris B). Further observations revealed that Polaris Aa is a classic Cepheid variable, a stellar class that pulses regularly.

For most of the 20th century, records indicate that the pulsation period has been increasing while the pulsation amplitude has been declining. But recently, this changed as the pulsation period started getting shorter while the amplitude of the velocity variations stopped increasing. According to a new study by Guillermo Torres, an astronomer with the Harvard & Smithsonian Center for Astrophysics (CfA), these behaviors could be attributed to long-term changes related to the binary nature of the system, where the two stars get closer to each other, and the secondary perturbs the atmosphere of the primary.

September 8, 2023September 8, 2023 by Evan Gough

A Black Hole Nibbles on a Star Every 22 Days, Slowly Consuming it

A star is ripped apart by a black hole. Credit: Mark Garlick

Astronomers working with NASA’s Neil Gehrels Swift Observatory have spotted something unusual. The observatory’s X-Ray Telescope (XRT) has captured emissions from a supermassive black hole (SMBH) in a galaxy about 500 million light-years away. The black hole is repeatedly feeding on an unfortunate star that came too close.

September 8, 2023September 14, 2023 by Jon Voisey

A Medieval Manuscript Likely Hides a Record of an Impending Recurrent Nova

Approximately every 80 years, a faint 10th magnitude star in the constellation of Corona Borealis dramatically increases its brightness. This star, T CrB, is known as a recurrent nova and last flared in 1946, peaking at magnitude 2.0, temporarily making it one of the 50 brightest stars in the night sky.

Aside from the 1946 eruption, the only other confirmed observation of this star’s outburst was in 1866. But new research by Dr. Bradley Schaefer suggests that a medieval monk may have spied T CrB brightening in 1217.

September 8, 2023September 8, 2023 by David Dickinson

Follow the Fall 2023 Return of Comet 103P Hartley

Comet Hartley — Comet 103/P Hartley encounters the Perseus Double Cluster in 2010. Image credit: Kevin Jung

Catch periodic cosmic interloper 103P Hartley while you can.

Periodic comets are like old friends, back for a visit. We have a get together with just such a denizen of the cometary league, as Comet 103P Hartley makes a favorable apparition in late 2023.

September 7, 2023September 7, 2023 by Jon Voisey

Did a Comet Airburst Destroy a Native American Community?

Artist impression of the Tunguska event.

In 1908, when an object entered the Earth’s atmosphere above the Podkamennaya Tunguska River, it flattened 80 million trees over nearly 2,200 square kilometers, and sent atmospheric shock waves reverberating around the world. Fortunately, this event was in a remote region and very few people were believed to be killed.

But research published in Nature’s Scientific Reports in 2022 by Tankersly et al. suggested that a similar, but even more powerful comet airburst in the Ohio River Valley may have been the death knell for the Hopewell civilization, some 1,600-1,700 years ago just outside modern day Cincinnati. However, other scientists rejected the arguments.

September 7, 2023September 7, 2023 by Matt Williams

Another New Way to Measure Distance in the Universe: Baryon Acoustic Oscillations

An artist's concept of the latest, highly accurate measurement of the Universe from BOSS. The spheres show the current size of the "baryon acoustic oscillations" (BAOs) from the early universe, which have helped to set the distribution of galaxies that we see in the universe today. Galaxies have a slight tendency to align along the edges of the spheres — the alignment has been greatly exaggerated in this illustration. BAOs can be used as a "standard ruler" (white line) to measure the distances to all the galaxies in the universe. Credit: Zosia Rostomian, Lawrence Berkeley National Laboratory

Measuring cosmic distances is a major challenge thanks to the fact that we live in a relativistic Universe. When astronomers observe distant objects, they are not just looking through space but also back in time. In addition, the cosmos has been expanding ever since it was born in the Big Bang, and that expansion is accelerating. Astronomers typically rely on one of two methods to measure cosmic distances (known as the Cosmic Distance Ladder). On the one hand, astronomers rely on redshift measurements of the Cosmic Microwave Background (CMB) to determine cosmological distances.

Conversely, they will rely on local observations using parallax measurements, variable stars, and supernovae. Unfortunately, there is a discrepancy between redshift measurements of the CMB and local measurements, leading to what is known as the Hubble Tension. To address this, a team of astronomers from several Chinese universities and the University of Cordoba conducted a two-year statistical analysis of one million galaxies. From this, they’ve developed a new technique that relies on Baryon Acoustic Oscillations (BAO) to determine distances with a greater degree of precision.

September 6, 2023September 6, 2023 by Matt Williams

The Space Station is Getting Gigabit Internet

NASA's ILLUMA-T payload communicating with LCRD over laser signals. Credit: NASA/Dave Ryan

Aboard the International Space Station (ISS), astronauts and cosmonauts from many nations are performing vital research that will allow humans to live and work in space. For more than 20 years, the ISS has been a unique platform for conducting microgravity, biology, agriculture, and communications experiments. This includes the ISS broadband internet service, which transmits information at a rate of 600 megabits per second (Mbps) – ten times the global average for internet speeds!

In 2021, NASA’s Space Communications and Navigation (SCaN) began integrating a technology demonstrator aboard the ISS that will test optical (laser) communications and data transfer. This system currently consists of Laser Communications Relay Demonstration (LCRD) and will soon be upgraded with the addition of the Integrated LCRD Low Earth Orbit User Modem and Amplifier Terminal (ILLUMA-T). Once complete, this system will be the first two-way, end-to-end laser relay system, giving the ISS a gigabit internet connection!

September 6, 2023September 6, 2023 by Evan Gough

TESS Finds a Planet That Takes 482 Days to Orbit, the Widest it’s Seen so Far

An artist's rendition of the two planets and star in the TOI-4600 system. One of them has the longest orbit of any planet yet found by TESS. Image Credit: Tedi Vick

We’re rapidly learning that our Solar System, so familiar to us all, does not represent normal.

A couple of decades ago, we knew very little about other solar systems. Astronomers had discovered only a handful of exoplanets, especially around pulsars. But that all changed in the last few years.