Catch Comet C/2017 S3 PanSTARRS in Outburst

Comet S3 PanSTARRS
Comet S3 PanSTARRS
Comet C/2017 S3 PanSTARRS from July 22nd. Image credit and copyright: hodorgabor

Comets are one of those great question marks in observational astronomy. Though we can plot their orbits thanks to Newton and Kepler, just how bright they’ll be and whether or not they will fizzle or fade is always a big unknown, especially if they’re a dynamic newcomer from the Oort Cloud just visiting the inner solar system for the first time.

We had just such a surprise from a cosmic visitor over the past few weeks, as comet C/2017 S3 PanSTARRS erupted twice, brightening into binocular visibility. Discovered on December 23rd 2017 during the PanSTARRS survey based on Haleakala, Hawai’i, S3 PanSTARRS is on a long-period, hyperbolic orbit and is most likely a first time visitor to the inner solar system.

The orbital path of comet S3 PanSTARRS through the inner solar system. Credit NASA/JPL.

S3 PanSTARRS was not only rocked by two new outbursts in quick succession, but seems to have undergone a tail disconnection event just last week, leveling off its brightness at around +8 magnitude and holding. This puts it in the range of binoculars under dark skies, looking like a fuzzy globular that refuses to snap into focus as it currently glides through the constellation of Camelopardalis the Giraffe the dawn sky.

The path of comet S3 PanSTARRS through August. Credit: Starry Night.

As July closes out, the time to catch sight of Comet S3 PanSTARRS is now, before it’s lost in the Sun’s glare. From latitude 40 degrees north, the comet sits 20 degrees above the northeastern horizon, about an hour before sunrise. By August 7th however, it drops below 10 degrees altitude. From there, the comet begins to circle the Sun as seen from the Earth beginning to favor southern hemisphere observers at dawn, who may be able to track it straight through perihelion on August 16th, if its brightness holds up. From there, northern hemisphere viewers may get a second view at dawn in September, again, if its brightness holds.

The dawn path of the comet looking northeast at dawn from latitude 35 degrees north, from July 31st through the first week of August. Credit: Starry Night.

You never know when it comes to comets. Here’s a brief rundown of the celestial happenings for comet C/2017 S3 PanSTARRS:

August

3- Crosses into the constellation Gemini.

4- Passes near the bright star Castor.

5- Passes near the bright star Pollux.

7- Crosses into the constellation Cancer.

7- Passes closest to the Earth, at 0.758 Astronomical Units (AU) distant.

8- Crosses southward over the ecliptic plane.

9- Passes just 4 degrees from the Beehive cluster, M44.

11- Passes 2 degrees from the open cluster M67.

12- Passes 10.5 degrees from Sun (1st apparent close pass as seen from the Earth)

13- Crosses into the constellation Hydra.

15- Reaches maximum brightness: the comet may top +2nd magnitude in mid-August.

16- Reaches perihelion at 0.21 AU from the Sun.

18- Crosses into the constellation Sextans.

30-Crosses into the constellation Leo.

31-Crosses the ecliptic plane northward.

The projected light curve for comet S3 PanSTARRS. The black dots are actual observations. Credit Seiichi Yoshida.

September

3- passes 4 degrees from the Sun.

25- Crosses into the constellation Coma Berenices.

From there, Comet C/2017 S3 PanSTARRS drops back below 6th magnitude in September, then below 10th magnitude in October as it heads back off into the icy realms of the outer solar system.

Be sure to nab this icy interloper why you can. The quote comet hunter David Levy, “Comets are like cats… they have tails, and they do exactly what they want.”

Here Comes Comet Heinze for the Holidays

Comet C/2017 T1 Heinze passes near the galaxy NGC 2706 on November 25th. Image credit and copyright: Charles Bell.

Yeah, we’re still all waiting for that next great “Comet of the Century” to make its presence known. In the meantime, we’ve had a steady stream of good binocular comets over the past year both expected and new, including Comet C/2017 O1 ASASSN1, 45/P Honda-Mrkos-Pajdušáková and Comet 41P Tuttle-Giacobini-Kresák (links). Now, another newcomer is set to bring 2017 in over the finish line.

The Discovery: Astronomer Aren Heinze discovered Comet C/2017 T1 Heinze as a tiny +18th magnitude fuzzball on the night of October 2nd, 2017. The comet will juuust breech our “is interesting, take a look” +10th magnitude cutoff in the final weeks of December leading into January, perhaps topping out around +8th magnitude.

Heinze discovered his first comet as part of the Asteroid Terrestrial-Impact Last Alert System (ATLAS) search program looking for hazardous objects using the eight 50 cm Wright-Schmidt telescope array atop Haleakala and Mauna Loa in the Hawaiian Islands.

The passage of Comet Heinze through the inner solar system. Credit: NASA/JPL

The orbit for Comet Heinze is an intriguing one, and as is often the case with comets, tempts us with what could have been. Heinze will vault over the ecliptic headed northward on Christmas Day, and reaches perihelion 87 million km (0.58 AU) from the Sun on February 21st, 2018. Closest passage from Earth for Comet Heinze is 33 million km (0.22 AU) on January 4th, 2018, when the comet will appear to move an amazing seven degrees a day through the constellation Camelopardalis.

But it’s the southward passage of Heinze though the ecliptic on April 1st that gives us pause, only 0.0144 AU exterior of Earth’s orbit… had this occurred on July 4th, we might’ve been in for a show, with the comet only 2.1 million kilometers away! Heinze seems like a tiny body as comets go, and there’s discussion that the comet is dynamically new and may end up shredding its nucleus all together. (link)

On a steep 97 degree inclined retrograde orbit, Comet Heinze also has a knife edge hyperbolic eccentricity of nearly 1.0. As with many long period comet, it’s tough to tell if Comet Heinze is a true denizen of our solar system, or just visiting. 2017 also saw the first asteroid whose extra-solar source was clear, as I/2017 U1 ‘Oumuamua, which passed through the inner solar system this past October.

The December path of Comet Heinze. Starry Night.

The Prospects: Currently, Comet Heinze is located highest to the south around 5AM local for northern hemisphere observers. Expect this situation to change to around 2 AM towards months end, as the comet is higher placed in the constellation Lynx come January 1st, 2018 as it nears opposition.

Comet observer Charles Bell noted on November 27th that Comet Heinze currently displays a short fan-shaped tail, about 88 days before perihelion.

Here’s the blow-by-blow for Comet Heinze for the next few months (passages mentioned here are to within a degree unless otherwise noted).

December

7- Crosses the celestial equator northward.

16- Passes near +3 magnitude star Zeta Hydrae.

18- Crosses into the constellation Cancer.

21- Passes near the open cluster M67.

25- Photo op: passes near the Beehive Cluster M44 and crosses the ecliptic northward.

29- Skirts the corner of the constellation Gemini and crosses into the Lynx.

The January 2018 passage of Comet Heinze through the inner solar system. Starry Night

January

1- May break +10th magnitude?

1- Passes near the +4.5 magnitude star 21 Lyncis.

2- Reaches opposition.

3- Passes near the +4.5 magnitude star 2 Lyncis and into the constellation Camelopardalis.

5- Passes near the +4 magnitude star Alpha Camelopardalis.

6- Passes 31 degrees from the north celestial pole.

7- Crosses into the constellation Cassiopeia.

10-Crosses the galactic equator southward.

13- Crosses into the constellation Andromeda.

14-Crosses into the constellation Lacerta.

17- Passes near the +4.5 magnitude star 6 Lacertae.

21- Passes near the +4 magnitude star 1 Lacertae.

23- Crosses into the constellation Pegasus.

February

26- Passes near the globular cluster M15.

March

1- May drop back down below +10th magnitude?

heinze
The projected light curve for Comet Heinze. Credit: Seiichi Yoshida’s Weekly Info on Bright Comets.

And though Comet Heinze won’t join their ranks, here’s a list of the great comets of the past century:

You could say we’re due.

Surprise: Comet E4 Lovejoy Brightens

Comet C/2017 E4 Lovejoy from the morning of Monday, April 3rd, courtesy of Gianluca Masi. Credit and copyright: The Virtual Telescope Project

Had your fill of binocular comets yet? Thus far this year, we’ve had periodic comets 2P/Encke, 45P/Honda-Mrkos-Pajdušáková and 41P/Tuttle-Giacobini-Kresák all reach binocular visibility above +10th magnitude as forecasted. Now, we’d like to point out a surprise interloper in the dawn sky that you’re perhaps not watching, but should be: Comet C/2017 E4 Lovejoy.

If that name sounds familiar, that’s because E4 Lovejoy is the sixth discovery by prolific comet hunter Terry Lovejoy. Comets that have shared the Lovejoy moniker include the brilliant sungrazer C/2011 W3 Lovejoy, which amazed everyone by surviving its 140,000 kilometer (that’s about 1/3 the Earth-Moon distance!) pass near the blazing surface of the Sun on December 16th, 2011 and went on to be a great comet for southern hemisphere skies.

The path of Comet E4 Lovejoy through the end of April. Credit: Starry Night.

Unfortunately, E4 Lovejoy won’t get quite that bright, but it’s definitely an over achiever. Shining at a faint +15th magnitude when it was first discovered last month on March 9th, 2017, it has since jumped up to +7th magnitude (almost 160 times in brightness) in just a few short weeks. We easily picked it out near the +2.4 magnitude star Enif (Epsilon Pegasi) on Saturday morning April 1st in the pre-dawn sky. E4 Lovejoy was an easy catch with our Canon 15×45 image-stabilized binocs, and looked like a tiny +7 magnitude globular (similar to nearby Messier 15) that stubbornly refused to snap into focus. In fact, I’d say that E4 Lovejoy was a much easier comet to observe than faint Comet 41P/Tuttle-Giacobini-Kresák, which made its closest pass 0.142 Astronomical Units (21.2 million kilometers) from the Earth on the same day.

Comet E4 Lovejoy from the morning of April 4th. Image credit and copyright: Gerald Rhemann/Sky Vistas.

Prospects and Prognostications 

E4 Lovejoy will remain an early pre-dawn object through April for northern hemisphere observers as it glides through the constellations Pegasus, Andromeda and Triangulum. If current predictions hold true, the comet should reach a maximum brightness of magnitude +6 around April 15th. On an estimated ~ 600,000 year orbit, Comet E4 Lovejoy may be a first time visitor to the inner solar system, and its current outburst may also be short-lived. In fact, there’s lots of speculation that Comet E4 Lovejoy may disintegrate altogether, very soon. Plus, the Moon is headed towards Full next week on April 11th, making this week the best time to catch a glimpse of this fleeting comet.

The projected light curve for Comet E4 Lovejoy. Credit: Seiichi Yoshida’s Weekly Information About Bright Comets.

And to think: we just missed having a bright naked eye comet! That’s because Comet E4 Lovejoy very nearly passed through the space that the Earth will occupy just next month. In fact, the comet passed just 0.11 AU (17 million kilometers) interior to the Earth’s orbit on March 22nd, 2017. Had it done the same on May 4th, it would have been 5 times closer and 25 (about 3 to 4 magnitudes) times brighter!

The orbit of Comet E4 Lovejoy through the inner solar system. NASA/JPL

A tantalizing miss, for sure. Comet C/2017 E4 Lovejoy reaches perihelion at 0.5 AU (77.5 million kilometers) from the Sun on April 23rd, and passed 0.6 AU (93 million kilometers) from the Earth on March 31st. This week, it will be moving through Pegasus at a rate of about four degrees (8 Full Moon diameters) a day. With an orbital inclination of 88 degrees, Comet E4 Lovejoy’s path is very nearly perpendicular to the ecliptic path traced out by the Earth. The comet swung up from the south during discovery, and is now headed northward towards perihelion.

Here are some key dates for Comet C/2017 E4 Lovejoy to watch out for in April:

April 7th: Passes less than one degree from the +3.5 magnitude star Sadal Bari (Lambda Pegasi).

April 9th: Passes less than 10′ from the +2.4 magnitude star Scheat (Beta Pegasi).

April 13th: Crosses into the constellation Andromeda.

April 19th: Photo-op, as the comet passes 4 degrees from the Andromeda Galaxy M31.

April 22nd: Passes between the +2nd magnitude star Mirach and the +4th magnitude star Mu Andromedae.

April 27th: Passes five degrees from the Pinwheel Galaxy M33.

April 28th: Crosses into the constellation Triangulum.

Looking to the northeast at 6 pm local on the morning of April 19th from latitude 30 degrees north. Credit: Stellarium.

Teaser for 2017 Comets

We’re barely a quarter of the way through 2017, with more cometary action to come. We’re expecting 2015 ER51 PanSTARRS (May), and 2015 V2 Johnson (June) to reach binocular visibility. You can read about comets, occultations, and more in our guide to 101 Astronomical Events for 2017, a free e-book from Universe Today.

We’re due for the next big one, for sure. It always seems like there’s a “Great Comet” per every generation or so, and its been 20 years now since comets Hale-Bopp and Hyakutake graced northern skies.

Binoculars are the best tool for observing comets like E4 Lovejoy, as they offer a generous true (i.e. not inverted) field of view. A good finder chart and dark skies also help. We like to find a good nearby ‘anchor’ object such as a bright star, then hop into the suspected comet area and start sweeping.

One thing’s for sure: we need more comets with names like Lovejoy… if nothing else, it’s much easier to pronounce, and us science writers don’t have to keep hunting through the ‘insert’ menu for those strange letter symbols that grace many of these icy denizens of the Oort Cloud as they pay a visit to the inner solar system.