TRG – Telescope Review Guide

We have yet another new comet coming into view! Jointly discovered by amateur astronomers in South Korea and the United States, this comet is named Yi-SWAN; for the South Korean amateur astronomer who found it March 26 and the SWAN instrument aboard NASA’s solar satellite SOHO. It is not yet known whether Yi-SWAN will be a recurring comet or if it’s one and done.

Cassiopeia

Where can you find Yi-SWAN? Right now it’s flying through Cassiopeia. It’s still small and dim but you should be able to spot it with a backyard telescope such as the Orion SkyQuest XT8.

Orion SkyQuest XT8

It should appear as a small fuzzy green ball. It has not been observed to have a tail but that should change as the wanderer nears the Sun. After April 20, look for Yi-SWAN to be in Perseus. Yi-SWAN should be visible until mid-May when it will be too close to the sun to be seen by most observers.

There’s a new comet passing nearby and it’s name is Lulin. This is when and how to find it.

On the night of February 23rd, in a moonless sky and near its peak brightness, Comet Lulin passes 2° south-southwest of Saturn.

Lulin’s closest approach to Earth, 61 million km, occurs on February 24th, when the comet may be at a peak of magnitude 5.0. By now it’s high up by late evening.

On the night of February 25th the comet goes through opposition, nearly 180° from the Sun in our sky. This means there mght be an “opposition effect”

brightening of its dusty coma and dust tail!

Path of Comet Lulin during February

After that Lulin moves away from both Earth and the Sun, fading quickly. The evening of February 27 will see it at about 6th magnitude within 1° of Regulus. Moonlight starts interfering again around the 28th.

Tails and Antitails

Because the comet stays nearly on the ecliptic, its tail (which points away from the Sun) aligns with the ecliptic and with the comet’s own direction of motion across the sky.

Moreover, because Earth remains in the comet’s own orbital plane, we see the comet with a very thin tail and an antitail, a spike pointing in almost the opposite direction from the main tail. Why? In three dimensions a comet’s dust tail is often wide but it’s always thin, confined to the comet’s orbital plane. When we are in or near this plane, we can sometimes see parts of the wide, thin dust tail on opposite sides of the comet’s head. We pass through most comets’ orbital planes briefly. This time, the situation will last and last.

A comet’s blue-green gas tail, on the other hand, always points nearly in a straight line away from the Sun in space. Cometary gas is blown directly away from the Sun at high speed by the solar wind.

MARCH: Following Lulin Out

Comet Lulin crosses from Leo into Cancer at the beginning of March and, having passed opposition, is now better seen in the evening than the morning hours however observers will have to contend with moonlight from about March 1st through 11th.

As Comet Lulin recedes, its passage across our sky will slow.  By May’s end it will be lost in the afterglow of sunset.

Comet Lulin won’t return again to the inner solar system for more than a thousand years.