Searching for Extragalactic Supernovae

I'll soon be doing an extragalactic supernova search, monitoring a small group of 5 or 6 spiral galaxies, similar in structure, to our Milky Way, barred-spiral galaxy - in the Virgo galaxy cluster.

The Virgo Cluster of galaxies is (around) 30-50 million light-years from the "Local Group" - the Milky Way's home, galactic cluster. The Virgo galactic cluster contains a spiral galaxy, M66, in the constellation Leo. It is some 35+ million light-years distant.

Back on 11 February 1989, at around 02:15am EST, Insight Observatory Managing Member and Project Developer, Michael Petrasko, and I, independently co-discovered a supernova (SN1989b), within one of the outer spiral arms of M66 (Michael, was the actual discoverer; I just "looked"!).

The Local Group and other galaxy cluster groups. Graphic by Dale Alan Bryant.

Supernova events within any given galaxy are estimated to occur only two or three times in a century. I'll see if I can refine that estimate, somewhat, over the course of a few months of nightly or bi-nightly photographic time-exposures of the group, using one of Insight Observatory's remote astrographs (photographic telescope) - ATEO-1, or ATEO-2A. The instruments are situated in the western New Mexico region, respectively - some of the clearest and darkest skies in the world.

Typically, an SN burst is so energetic that its brilliance, temporarily, outshines the combined light of all of the billions of stars within a given galaxy. Any SN event will stand out as a tiny, bright, dot, superimposed against the overall, dim, oval blur of light of the main body of the galaxy. It is during a supernova burst that the heavy elements of our universe are forged (iron, nickel, and other heavy metals). From there, the energy of the blast disperses the elemental metals into the surrounding space including any nearby molecular clouds which ultimately condense and become planetary systems (such was the case in our "Solar" system).

This is the history of the metallic content of Earth's mantle and crust, and, its solid iron core.

Dale Alan Bryant
Senior Contributing Science Writer

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What's In The Sky - February 2020

Clear February nights present some great stargazing opportunities. Be sure to bundle up and keep warm while you get outside for some stargazing fun!

Here are a few of Orion Telescopes and Binoculars' top picks for February stargazing:

New Moon

February 23rd should be one of the best nights for deep-sky viewing as the New Moon phase will provide the darkest night of the short month. Use Orion Broadband Filters to enhance your view.

On the evening of Monday, February 9th, Mercury (orbit is shown as a red curve) will reach its widest separation, 18 degrees east of the sun. With Mercury sitting above a nearly vertical evening ecliptic, this will be the best appearance of the planet in 2020 for Northern Hemisphere observers. The optimal viewing times fall between 6 and 7 p.m. local time. Viewed in a telescope (inset), the planet will exhibit a waning half-illuminated phase. Image credit: Starry Night.

Mercury High In The Sky

On February 9th, Mercury will be at its greatest eastern elongation, meaning it is at its greatest separation from the Sun. Mercury will be at an altitude of approximately 16 degrees when the Sunsets at 17:34 PST, making it an ideal time to observe this tricky target.

Planetary Lineup Get up early on President's Day, February 17th, to see a lineup of three planets and the Moon. At dawn, the crescent Moon and Mars, Jupiter, and Saturn will form a line spanning about 39 degrees in the southeastern sky.

Before sunrise on the next day, February 18th, viewers in North America can watch the Moon occult Mars! Better yet, try snapping a sequence of high-magnification pics of the event.

Betelgeuse In The News

Betelgeuse has been in the news lately since dimming down to a magnitude of around 1.5, the lowest brightness in more than a century. The red supergiant is normally variable, but the unusual dimming has brought up the question of whether a supernova is imminent. Betelgeuse is close enough that if it went supernova it would be brighter than the full moon, a spectacular astronomical event. However, the consensus is that this probably won't be happening soon. The best estimate is sometime in the next 100,000 years, so it is more likely that this variability is normal, and we've still got a few millennia before the light show.

It may not be as flashy, but if you want to see a supernova now astronomer Koichi Itagaki discovered a supernova on January 12th. Located in the galaxy NGC 4636 in the constellation Virgo, it should be visible with a 6" or larger telescope. Referred to as SN2020ue, it is currently at magnitude 12.1 and should be visible under dark skies at around 60-100x magnification as a dim star just outside of the galaxy's core.

Galaxies M81 and M82 in Ursa Major - 5 x 300 Second LRGB Image by Insight Observatory.

Bright Galaxies

In late February, bright galaxies M81 and M82 will be about as high in the sky as they will get for North American stargazers. From a dark sky site, these galaxies are visible with a 50mm or larger binocular, but we suggest you use a large telescope to chase these galaxies down just off the leading edge of the Big Dipper asterism. Many observers consider M81 & M82 the best pairing of visual galaxies in the sky!

If you would like to receive image data of galaxies such as M81 and M82 and other deep-sky objects taken on the Astronomical Telescopes for Educational Outreach (ATEO), please visit Insight Observatory's Custom Image Data Request form.

All objects described above can easily be seen with the suggested equipment from a dark sky site, a viewing location some distance away from city lights where light pollution and when bright moonlight does not overpower the stars.

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Imaging Extragalactic Supernovae

Since the Astronomical Telescope for Educational Outreach (ATEO-1) went online back in May 2017, we have since had the chance to image galaxies and galaxy clusters with a 16" f/3.7 astrograph telescope. Besides using the remote robotic telescope for acquiring "pretty" pictures of deep-sky objects such as galaxies, it can also be used as a tool for gathering data for extragalactic supernovae search.

Professional astronomers distinguish between two main classes of supernovae. The distinctions have to do with the type of explosion occurring, how it is triggered, the resulting light curve, and the atomic elements visible in the spectrum of the supernova. However, for amateur astronomers’ purposes, we can consider two very basic types of a supernova: galactic and extragalactic. Our primary concern is with extragalactic supernovae, as a galactic supernova is far more infrequent an event than even a brilliant comet, solar eclipse, or any of a number of other “rare” astronomical phenomena. In fact, more than a dozen generations have passed without any human witnessing a supernova in our own Milky Way galaxy!

ASASSN-16cs/ SN 2016asf - Image Credit: PanSTARRS-1 Image Access

Imaging supernovae involve imaging galaxies as mentioned above. There are few other considerations than those normally applied to capturing a CCD image of a distant galaxy. Supernovae usually occupy the briefest time span of the three main transient events discussed in this section. Comets are often visible for weeks or even months, and even rapidly-moving near-Earth asteroids stick around for a week or more. Supernovae, on the other hand, may last only a few nights, appearing as a single brilliant star outshining the light of 100 billion companions in its host galaxy.

There is a list published online by the Central Bureau for Astronomical Telegrams that gives the latest discoveries and the name of the host galaxy (or position if the host galaxy is uncataloged). Due to the short time available to image supernovae, subscribing to the IAU Circular is recommended as well. This email circular lists recent astronomical headlines including supernovae, novae, comets, interesting asteroids, and other events. Often the information in the circular is not available immediately through any other source.

Photometric (brightness) measurements can be made of a supernova as it fades. This information tells scientists about the type of explosion and can even lead to information about the distance to the host galaxy of the redshift (recessional velocity) of that galaxy, leading to a better understanding of the universe.

ASASSN-16cs Extragalactic Supernova Confirmation (Right) - Image by Isaac Cruz.

One of our neighbors at SkyPi Remote Observatory, Isaac Cruz, discovered an extragalactic supernova on March 7, 2016. This one was in the constellation of Gemini (The Twins). Isaac received a notification of a transient from the ASASSN system from Ohio State University. Isaac stated, "Luckily I've been given the opportunity to do remote observing from the great folks at SkyPi Remote Observatory in New Mexico so this was the perfect time to do it." Isaac connected to his remote system and pointed the telescope to the given coordinates. He took a 10-second image at 1/3 the resolution (Bin 3) and the supernova was obvious just south of the galaxy. Discovery! Isaac then took a 10-minute image at full resolution and sent it for verification. In a few minutes, he received the confirmation that the new star had been certified and designated ASASSN-16cs and SN 2016asf.

Now that our hosting neighbor at SkyPi Remote Observatory has proven this type of discovery is possible with remote robotic telescopes, it has inspired us to craft an extragalactic supernova search program of our own that would allow students and individual users of the ATEO network to participate in such an endeavor.

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