How to see Mercury, the moon and the Gemini twins pass close together in the night sky this week
During the final week of June and continuing into the first week of July, we'll have a fair chance at sighting Mercury, the innermost planet to the sun.
Many people have never noticed that Mercury swings rapidly back and forth relative to the sun in our sky, while moving along in an orbit scarcely more than half as far from the sun as Venus.
This fastest-moving and smallest major planet (only 1.4 times wider than the moon) orbits the sun 4.15 times a year, but from our own moving vantage point it appears to go around only 3.15 times. Each year it makes about 3.5 swings into the morning sky and as many times into the evening — excursions of highly unequal character because of its eccentric orbit and the varying angles from which we view it.
Typically, as seen from the Northern Hemisphere for after-sunset views of Mercury, its spring treks into the evening skies prove to be the best. Although it did not occur officially within the spring season, this year's first evening apparition that ran from Feb. 23 through March 15 was an excellent one, since for a few days centered around the date of its greatest elongation from the sun (March 8), Mercury set just after the end of evening twilight against a dark sky.
Now, this speedy, rocky little world is again available to view in the evening sky, although on this occasion, not a "spring" apparition, but more like early summer, encompassing the timeframe from June 20 through July 11. This time, Mercury's greatest elongation from the sun will come on July 4. During this current evening apparition, Mercury's climb out of the west-northwest horizon comes at a steeper angle and yet it will attain an altitude essentially as high above the setting sun as it did in late February and early March.
What is different this time around is that it is now early summer, not late winter. So, from mid-northern latitudes, the duration of evening twilight is longer by about 30 minutes. As such, unlike in early March, we cannot hope to glimpse Mercury against a dark sky.
However, during its evening appearances, Mercury always appears brightest in the days leading up to its greatest elongation. On June 20, it shone at magnitude -0.2, brighter than the similarly-hued star Arcturus, the second brightest behind Sirius as seen from northern latitudes. By July 3 it will have faded to a still respectably bright magnitude of +0.5, which would rank it among the top ten brightest stars in the sky. So, it should not be too difficult to sight against the twilight sky, low in the west-northwest about 45 minutes to one hour after sunset.
And during this week, we'll have some help in identifying it thanks to some other celestial landmarks.
TOP TELESCOPE PICK:
Want to get close-up views of planets in the night sky? The Celestron NexStar 4SE is ideal for beginners wanting quality, reliable and quick views of celestial objects. For a more in-depth look at our Celestron NexStar 4SE review.
On Tuesday evening, June 24, Mercury will form a nearly straight line with two bright stars; the Gemini Twins, Pollux and Castor. Going from right to left, the distance between Castor and Pollux measures 4.5 degrees. If you were to draw an imaginary line between these two stars and extend it another 6.5 degrees to the left, you will come to Mercury.
Or, put another way, if you make a clenched fist and hold it out at arm's length, that will measure roughly 10 degrees. The distance from Mercury to the star Castor (going from left to right) should measure a bit more than one fist width, or about 11 degrees.
In addition, keep in mind that Mercury will appear much brighter than either Pollux and Castor. On this night, Mercury will shine at zero magnitude, while Pollux will appear only about a third as bright at magnitude +1.1 and Castor only about one quarter as bright at magnitude +1.6. So, while it's likely that you'll be able to see Mercury with your naked eye, Pollux and Castor will likely be more difficult to see amidst the twilight glow. So be sure to have a pair of binoculars on hand to help you see these Twin Stars teamed up with Mercury.
Remember: if you're looking for a telescope or binoculars to observe Mercury or any other night sky event, our guides for the best binoculars deals and the best telescope deals now can help.
Two evenings later, on Thursday, June 26, another celestial wanderer will appear on the scene — the moon. Only a little over 1.5 days past the new moon phase, it will appear as a very narrow, wire-thin crescent, a mere 3 percent illuminated by the sun. Here again, binoculars will prove most beneficial in helping to find not only Pollux and Castor, but this exceedingly slender lunar sliver.
But what an amazing scene awaits you if you are successful in making a sighting.
On this evening, Pollux and Castor will be pointing directly at the moon and the gap separating this trio will be equidistant: From Castor to Pollux will measure 4.5 degrees and from Pollux to the moon will measure another 4.5 degrees; a celestial triple play.
But don't forget Mercury.
It will be shining about 4.3 degrees to the left and ever-so-slightly above the moon. In short, four prominent celestial objects — the moon, a bright planet and two bright stars — stretched out across a little more than a dozen degrees of the west-northwest sky.
A celestial quadruple grouping!
But please keep in mind that in many parts of the country, June has a reputation for being a sultry, hazy and humid month. So unfortunately, visibility of objects so low to the horizon might hinder seeing this "celestial summit meeting." But if your local sky is clear and transparent, try not to miss it, for gatherings like this of the moon accompanied by bright stars and planets are unusual and wonderful sights.
Mercury will quickly move away from the Gemini Twins in the days following June 26, and will rapidly fade after July 4, transitioning into the morning sky on July 31. On balmy mornings in August, get up early to see this elusive planet climbing almost straight up above the point of sunrise.
By Aug. 19, about an hour before sunrise, it will reach its highest, with the "dynamic duo" of Venus and Jupiter, respectively 15 and 22 degrees higher still. Pollux and Castor will also be nearby and on the mornings of Aug. 20 and 21, the moon will again join in too!
Mark your calendars ...
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, Sky and Telescope and other publications.
Hashtags
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
CNN
an hour ago
- CNN
On GPS: The Trump administration's war on science
Secretary of Health and Human Services Robert F. Kennedy Jr. announced that he is cutting nearly half a billion dollars in federally funded mRNA vaccine research. Fareed speaks with former Baltimore Health Commissioner Dr. Leana Wen about the promises of mRNA technology for treating infectious diseases and the impact of cuts on America's scientists.
Wall Street Journal
an hour ago
- Wall Street Journal
Pump the Brakes on E-Bikes
I applaud the efforts in New York City to adopt an e-bike speed limit of 15 miles per hour, paralleling safety actions abroad ('New York Has a New E-Bike Speed Limit—and Can't Enforce It,' Page One, Aug. 8). Scientific literature from Europe, Asia and the Middle East documents the severe neurosurgical, orthopedic, maxillofacial and other traumatic injuries associated with the higher rate of speed for e-bikes compared to traditional pedal bicycles. The U.S. should learn from this experience and spare the public repeated tragedies. New York can continue to lead the way by implementing new requirements for licensure and registration for those e-bikes that travel at higher speeds more closely resembling mopeds and motorcycles. This will enable law enforcement to identify these vehicles in traffic flow and restrict their use to the roadway instead of bike lanes and sidewalks, where they are more likely to collide with pedestrians in densely populated areas.
Yahoo
an hour ago
- Yahoo
James Webb Finds Evidence of Free-Floating Planets So Large They Can Gather Their Own Planetary Systems
So much for heliocentrism. An international team of astronomers using observations made with the James Webb Space Telescope have found evidence of massive planets out there that're capable of forming their own planetary systems — without a star. These planets would be the center of something like a mini version of our solar system where other, smaller planets revolve around it. But without the light of a star, these systems, if they exist, would go largely overlooked by our telescopes, lost to the dark void of space. The work, a new study accepted for publication in the The Astronomical Journal, focuses on free-floating "rogue" planets which are not gravitationally bound to a star. While some rogue planets are first formed around a stellar object before being ejected from their system, the astronomers believe these ones may have formed from the same mechanism that gives birth to stars. "These discoveries show that the building blocks for forming planets can be found even around objects that are barely larger than Jupiter and drifting alone in space," lead author Belinda Damian, an astronomer at the University of St Andrews in Scotland, said in a statement about the work. "This means that the formation of planetary systems is not exclusive to stars but might also work around lonely starless worlds." Using James Webb observations taken between August and October 2024, the astronomers examined eight free-floating planets. With masses between five to ten times that of Jupiter, these belong to a class of objects believed to be the lowest mass objects that form from the collapse of the giant gas clouds that are sometimes referred to as stellar nurseries, as they're typically associated with star formation. For one reason or another, these objects didn't accumulate enough mass to sustain nuclear fusion reactions in their cores and become proper stars. These shouldn't be confused with brown dwarfs, however, which are much more massive substellar objects that are dozens of times heavier than Jupiter that also fail to kickstart nuclear fusion, earning them the moniker of "failed" stars. In this latest work, the astronomers detected excess emissions in the infrared spectra of these objects, showing that six of them have emissions associated with warm dust. This indicates the presence of a disk, or a circumstellar cloud of gas and dust that surrounds the planet. In itself, this isn't unusual, and such disks have been detected around rogue planets before. Around stars, these disks, referred to as protoplanetary disks, are where dense regions of gas and dust can coalesce to form planets, and are the leftover material from the star's formation which didn't get sucked into its collapsing core. But the kicker here is that the scientists have detected signs that the rogue planets' disks are already exhibiting the crucial first steps of planetary formation in the form of harboring silicate grains, which appear to be growing and crystallizing. These dusty grains can clump together to form planetesimals, the large, solid objects that are the building blocks of a baby planet. This is the first detection of silicate grains around a planetary mass object, the authors said. And it pairs tantalizingly with their previous study which showed that the rogue planet disks can last for millions of years, providing more than enough time to incubate inchoate worlds. "Taken together, these studies show that objects with masses comparable to those of giant planets have the potential to form their own miniature planetary systems," coauthor Aleks Scholz, who is also a St Andrews astronomer, said in the statement. "Those systems could be like the solar system, just scaled down by a factor of 100 or more in mass and size. Whether or not such systems actually exist remains to be shown." Ironically, then, maybe our ancestors weren't totally off the mark with their whole geocentrism fixation — they just had the wrong planetary system in mind. More on exoplanets: James Webb Spots Planets Forming Into Solar System in Real Time, Like an Organism's First Cells Solve the daily Crossword
